This "insulator' is about 4 inches tall and is threaded on the outside. It is embossed;
7500 VOLTS
PYREX
T.M.REG.
MADE IN U.S.A.
A
It also has an oblong opening in the bottom.
What is it and what was it used for?

Comments

An unusual insulator, used for isolating the high voltage electrodes. This one is made by the venerable American manufacturer Pyrex. Embossing is always a plus, since there is often none on these more unusual early industrial pieces, and the Pyrex name certainly adds appeal.

Ian Macky, 4 years agoIt's a neon sign insulator. You can see it in my Pyrex neon sign catalog here: <http://glassian.org/Pyrex/Neon/fcover.html>